Rac1 inhibitor NSC23766 blocks cofilin dephosphorylation but did not affect LIMK1 phosphorylation induced by thrombin. Effect of NSC23766 on cofilin (A) and LIMK-1 (Thr508; B) phosphorylation during platelet aggregation induced by 0.5 U/mL thrombin. Lysates of platelet stimulated with thrombin in the absence (-■-) or presence (-□-) of NSC23766 were immunoblotted with anti–phospho-cofilin, anti-cofilin anti–phospho-LIMK1/2, and anti-LIMK1 antibodies, and changes were estimated densitometrically. Graphic representation of the results. Values are the mean + SD or mean − SD for 3 independent experiments. Inset, representative immunoblots of cofilin phosphorylation.